This invention generally relates to milling cutters, and is specifically concerned with a milling cutter capable of cutting a workpiece in both right and left-handed rotary directions.
Milling cutters for cutting and shaping metal workpieces have been known in the prior art for many years. Such milling cutters generally comprise a cylindrical cutter body having a plurality of insert seats spaced around its outer periphery. Cutting inserts can be mounted within the insert seats by means of metal wedges, which are often secured to the cutter body by screws. In the vast majority of prior art milling cutters, the insert seats are oriented so that the inserts mounted therein will effectively cut a workpiece when the cutter body is rotated in a right-handed or counterclockwise direction as viewed from the cutting end of the cutter. The right-handedness of most milling cutters follows from the fact that most drive trains for such cutters are designed to rotate in a counterclockwise direction.
While most manufacturing concerns have traditionally preferred the use of right-handed milling cutters to perform their particular workpiece shaping operations, there is a growing demand for left-handed milling cutters. For example, in some of the machining operations presently used in the manufacture of engine blocks in the automotive industry, it is desirable for two or more milling cutters to simultaneously cut and shape opposite ends of the metal forming the block. It is further desirable that the cutting insert mounted in both of the cutters should cut the metal in what is known in the art as a "climb milling" orientation wherein the metal chips are cut to maximum thickness at the time the cutting edge of each insert initially engages the workpiece, in contrast to a "conventional milling" orientation, wherein there is a zero chip thickness when the cutting edge of each insert initially engages the workpiece. Such a climb milling orientation is preferred as it reduces the friction associated with the cutting operation, and extends the lives of the inserts mounted in the cutter body. However, if two right-handed milling cutters are simultaneously used to machine opposite ends of, for example, a metal workpiece being shaped into an engine block, one of the cutters will have to engage the metal workpiece in a disadvantageous conventional milling orientation.
As a right-handed cutter cannot effectively cut in a left-handed rotary direction due to the highly negative rake angles that the cutting inserts would present to the work surface, left-handed milling cutters have been developed to allow metal fabricators to perform such opposite ended cutting operations. However, due to the limited production runs of left-handed cutters, they are generally more expensive to purchase or replace than right-handed milling cutters. The manufacturing concern that purchases a number of such left-handed cutters to perform a specialized cutting operation may have no use for such cutters after the production run that necessitated the purchase has ended. Hence the conventional solution of merely purchasing and using left-handed cutters whenever the need arises is always expensive, and often inefficient as it ultimately results in the carrying of an inventory of infrequently used left-handed milling cutters.
Clearly there is a need for an ambidextrous milling cutter that is easily and conveniently capable of cutting metal in either a right or left-handed rotary direction. Such a cutter should be able to easily and effectively secure cutting inserts in either a left or right-handed orientation around the periphery of the cutter body. Finally, some sort of means should be provided for easily and conveniently changing the inserts from a right to a left-handed orientation and vice versa on the cutter body with a maximum amount of mechanical security, and a minimum expenditure of time, effort, and parts.